Add Claude AI-powered response validation and update test model

Changes:
1. Update quick test to use gemma3:4b (was gemma2:2b)
   - Increased timeout to 60s for larger model

2. Implement Claude headless validation (validate.go)
   - Hybrid approach: simple checks first, then Claude validation ALWAYS runs
   - Claude validates response quality, coherence, relevance
   - Detects gibberish, errors, and malformed responses
   - Falls back to simple validation if Claude CLI unavailable
   - Verbose logging shows Claude validation results

3. Validation flow:
   - Step 1: Fast checks (empty response, token count)
   - Step 2: Claude AI analysis (runs regardless of simple check)
   - Claude result overrides simple checks
   - If Claude unavailable, uses simple validation only

4. Workflow improvements:
   - Remove useless GPU memory check step (server already stopped)
   - Cleaner workflow output

Benefits:
- Intelligent response quality validation
- Catches subtle issues (gibberish, off-topic responses)
- Better than hardcoded pattern matching
- Graceful degradation when Claude unavailable

cmd/test-runner/main.go

@@ -148,7 +148,7 @@ func runTests(configPath, profileName, ollamaBin, outputPath string, verbose, ke
 	// Run tests
 	startTime := time.Now()
 	tester := NewModelTester(server.BaseURL())
-	validator := NewValidator(config.Validation, monitor)
+	validator := NewValidator(config.Validation, monitor, verbose)
 
 	results := make([]TestResult, 0, len(profile.Models))